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Paper is a thin sheet material produced by mechanically or chemically processing cellulose derived from wood, Textile, poaceae, herbivore dung, or other vegetable sources in water. Once the water is drained through a fine mesh leaving the fibre evenly distributed on the surface, it can be pressed and dried.
The papermaking process developed in east Asia, probably China, at least as early as 105 Common Era,Hogben, Lancelot. "Printing, Paper and Playing Cards". Bennett, Paul A. (ed.) Books and Printing: A Treasury for Typophiles. New York: The World Publishing Company, 1951. pp. 15–31. p. 17. & Mann, George. Print: A Manual for Librarians and Students Describing in Detail the History, Methods, and Applications of Printing and Paper Making. London: Grafton & Co., 1952. p. 77 by the Han Dynasty court eunuch Cai Lun, although the earliest archaeological fragments of paper derive from the 2nd century BCE in China.
Although paper was originally made in single sheets by hand, today it is mass-produced on large machines—some making reels 10 metres wide, running at 2,000 metres per minute and up to 600,000 tonnes a year. It is a versatile material with many uses, including printing, painting, graphics, signage, design, packaging, decorating, writing, and Housekeeping. It may also be used as filter paper, wallpaper, book endpaper, conservation paper, laminated worktops, toilet tissue, currency, and security paper, or in a number of industrial and construction processes.
It has been said that knowledge of papermaking was passed to the Islamic world after the Battle of Talas in 751 CE when two Chinese papermakers were captured as prisoners and used to extract 'the secrets' of papermaking. Although the veracity of this story is uncertain, paper started to be made in Samarkand soon after. In the 13th century, the knowledge and uses of paper spread from the Middle East to medieval Europe, where the first water-powered were built. Because paper was introduced to the West through the city of Baghdad, it was first called bagdatikos.Murray, Stuart A. P. The Library: An illustrated History. Skyhorse Publishing, 2009, p. 57. In the 19th century, industrialization greatly reduced the cost of manufacturing paper. In 1844, the Canadian inventor Charles Fenerty and the German inventor Friedrich Gottlob Keller independently developed processes for pulping wood fibres.
There are three main chemical pulping processes: the sulfite process dates back to the 1840s and was the dominant method before the second world war. The kraft process, invented in the 1870s and first used in the 1890s, is now the most commonly practised strategy; one of its advantages is the chemical reaction with lignin produces heat, which can be used to run a generator. Most pulping operations using the kraft process are net contributors to the electricity grid or use the electricity to run an adjacent paper mill. Another advantage is that this process recovers and reuses all inorganic chemical reagents. Soda pulping is another specialty process used to pulp , bagasse and hardwoods with high silicate content.
There are three main classifications of recycled fibre:
Recycled papers can be made from 100% recycled materials or blended with virgin pulp, although they are (generally) not as strong nor as bright as papers made from the latter.
Pressing the sheet removes the water by force. Once the water is forced from the sheet, a special kind of felt, which is not to be confused with the traditional one, is used to collect the water. When making paper by hand, a blotter sheet is used instead.
Drying involves using air or heat to remove water from the paper sheets. In the earliest days of papermaking, this was done by hanging the sheets like laundry; in more modern times, various forms of heated drying mechanisms are used. On the paper machine, the most common is the steam-heated can dryer. These can reach temperatures above and are used in long sequences of more than forty cans where the heat produced by these can easily dry the paper to less than six percent moisture.
Paper at this point is uncoated. Coated paper has a thin layer of material such as calcium carbonate or china clay applied to one or both sides in order to create a surface more suitable for high-resolution halftone screens. (Uncoated papers are rarely suitable for screens above 150 lpi.) Coated or uncoated papers may have their surfaces polished by . Coated papers are divided into matte, semi-matte or silk, and gloss. Gloss papers give the highest optical density in the printed image.
The paper is then fed onto reels if it is to be used on web printing presses, or cut into sheets for other printing processes or other purposes. The fibres in the paper basically run in the machine direction. Sheets are usually cut "long-grain", i.e. with the grain parallel to the longer dimension of the sheet. Continuous form paper (or continuous stationery) is cut to width with holes punched at the edges, and folded into stacks.
Wove paper does not exhibit "laidlines", which are small regular lines left behind on paper when it was handmade in a mould made from rows of metal wires or bamboo. Laidlines are very close together. They run perpendicular to the "chainlines", which are further apart. Handmade paper similarly exhibits "deckle edges", or rough and feathery borders. "ARCHIVED – Introduction – Detecting the Truth. Fakes, Forgeries and Trickery – Library and Archives Canada" in a virtual museum exhibition at Library and Archives Canada
It is estimated that paper-based storage solutions captured 0.33% of the total in 1986 and only 0.007% in 2007, even though in absolute terms the world's capacity to store information on paper increased from 8.7 to 19.4 . "The World's Technological Capacity to Store, Communicate, and Compute Information" , especially Supporting online material , Martin Hilbert and Priscila López (2011), Science, 332(6025), 60–65; free access to the article through here: martinhilbert.net/WorldInfoCapacity.html It is estimated that in 1986 paper-based postal letters represented less than 0.05% of the world's telecommunication capacity, with sharply decreasing tendency after the massive introduction of digital technologies.
Paper has a major role in the visual arts. It is used by itself to form two- and three-dimensional shapes and . It has also evolved to being a structural material used in furniture design. Watercolor paper has a long history of production and use.
Paper is often characterized by weight. In the United States, the weight is the weight of a ream (bundle of 500 sheets) of varying "basic sizes" before the paper is cut into the size it is sold to end customers. For example, a ream of 20 lb, paper weighs 5 pounds because it has been cut from larger sheets into four pieces. In the United States, printing paper is generally 20 lb, 24 lb, 28 lb, or 32 lb at most. Cover stock is generally 68 lb, and 110 lb or more is considered card stock.
In Europe and other regions using the ISO 216 paper-sizing system, the weight is expressed in grams per square metre (g/m2 or usually gsm) of the paper. Printing paper is generally between 60 gsm and 120 gsm. Anything heavier than 160 gsm is considered card. The weight of a ream therefore depends on the dimensions of the paper and its thickness.
Most commercial paper sold in North America is cut to standard based on customary units and is defined by the length and width of a sheet of paper.
The ISO 216 system used in most other countries is based on the surface area of a sheet of paper, not on a sheet's width and length. It was first adopted in Germany in 1922 and generally spread as nations adopted the metric system. The largest standard size paper is A0 (A zero), measuring one square metre (approx. 1189 × 841 mm). A1 is half the size of a sheet of A0 (i.e., 594 mm × 841 mm), such that two sheets of A1 placed side by side are equal to one sheet of A0. A2 is half the size of a sheet of A1, and so forth. Common sizes used in the office and the home are A4 and A3 (A3 is the size of two A4 sheets).
The density of paper ranges from for tissue paper to for some specialty paper. Printing paper is about .
Paper may be classified into seven categories:
Some paper types include:
Paper made from mechanical pulp contains significant amounts of lignin, a major component in wood. In the presence of light and oxygen, lignin reacts to give yellow materials, which is why newsprint and other mechanical paper yellows with age. Paper made from bleached kraft process or sulfite process pulps does not contain significant amounts of lignin and is therefore better suited for books, documents and other applications where whiteness of the paper is essential.
Paper made from wood pulp is not necessarily less durable than a rag paper. The aging behaviour of a paper is determined by its manufacture, not the original source of the fibres. Furthermore, tests sponsored by the Library of Congress prove that all paper is at risk of acid decay, because cellulose itself produces formic, acetic, lactic and oxalic acids.
Mechanical pulping yields almost a tonne of pulp per tonne of dry wood used, which is why mechanical pulps are sometimes referred to as "high yield" pulps. With almost twice the yield as chemical pulping, mechanical pulps is often cheaper. Mass-market paperback books and newspapers tend to use mechanical papers. Book publishers tend to use acid-free paper, made from fully bleached chemical pulps for hardback and Trade paperbacks books.
Worldwide consumption of paper has risen by 400% in the past 40 years leading to increase in deforestation, with 35% of harvested trees being used for paper manufacture. Most paper companies also plant trees to help regrow forests. Logging of old growth forests accounts for less than 10% of wood pulp, but is one of the most controversial issues.
Paper waste accounts for up to 40% of total waste produced in the United States each year, which adds up to 71.6 million tons of paper waste per year in the United States alone. The average office worker in the US prints 31 pages every day.Groll, T. 2015 In vielen Büros wird unnötig viel ausgedruckt , Zeit Online, 20 June 2015. Americans also use in the order of 16 billion per year.
Conventional bleaching of wood pulp using elemental chlorine produces and releases into the environment large amounts of organochloride, including chlorinated dioxins. Pdf Dioxins are recognized as a persistent environmental pollutant, regulated internationally by the Stockholm Convention on Persistent Organic Pollutants. Dioxins are highly toxic, and health effects on humans include reproductive, developmental, immune and hormonal problems. They are known to be carcinogenic. Over 90% of human exposure is through food, primarily meat, dairy, fish and shellfish, as dioxins accumulate in the food chain in the fatty tissue of animals.
The paper pulp and print industries emitted together about 1% of world greenhouse-gas emissions in 2010 and about 0.9% in 2012.
FAO figures for 2021 show the production of graphic papers continuing its decline from a mid-2000s peak to hover below 100 million tonnes a year. By contrast, the production of other papers and paperboard – which includes cardboard and sanitary products – has continued to soar, exceeding 320 million tonnes.
FAO has documented the expanding production of cardboard in paper and paperboard, which has been increasing in response to the spread of e-commerce since the 2010s. Data from FAO suggest that it has been even further boosted by COVID-19-related lockdowns.
With increasing environmental concerns about synthetic coatings (such as PFOA) and the higher prices of hydrocarbon based petrochemicals, there is a focus on zein (corn protein) as a coating for paper in high grease applications such as popcorn bags.
Also, synthetics such as Tyvek and Teslin have been introduced as printing media as a more durable material than paper.
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